Active restraint systems for automobile vehicle passengers include three-point seat belt restraints that are integrated with each vehicle passenger seat. One end of the seat belt typically is fastened to a side pillar anchor point on one side of the passenger compartment by means of a belt retraction assembly. The other end of the seat belt typically is secured fast to the vehicle body structure by a permanent anchor bolt. The intermediate portion of the seat belt is trained through a D-ring, which in turn is secured typically to an upper portion of the structural side pillar of the automotive vehicle body. The intermediate portion is adapted to be buckled to a third anchor member on the floor pan of the passenger compartment. This permits the seat belt to be trained over the front torso of a belted passenger as well as over the pelvic region. Examples of such three-point type seat belt restraint systems can be seen by referring to U.S. Pat. Nos. 4,645,232, 4,955,639 and 5,529,344. These patents are representative of the existing state of the art.
A three-point seat belt anchorage of this kind makes it necessary for an anchor bolt for the D-ring, through which the seat belt is trained, to be located at an upper location on the structural side pillar of the automotive body in rather close proximity to the head of a belted passenger. Because of this three-point seat belt restraint geometry, it is beneficial to provide enhanced protection for the vehicle occupant against head injuries caused by high-energy impact forces to which the vehicle body may be subjected during accidents on the roadway.
It is known design practice to provide for energy absorption of impact forces that might be applied to the seat belt anchorage at the upper portion of the structural side pillar of an automotive vehicle passenger compartment when the impact force is in the direction of the axis of the anchor bolt for the seat belt D-ring. An example of such an energy-absorbing device is shown in U.S. Pat. No. 5,529,344 where a metallic bellows is situated between the seat belt D-ring and a structural side member of the vehicle body. When an axial load is applied to the seat belt anchor, the metallic bellows will be crushed, thereby absorbing the kinetic energy of the impact force applied to the head of the bolt.
It is known design practice also to provide a protective cover for an anchor bolt at the upper portion of the structural pillar of an automotive vehicle body wherein the protective cover includes a deformable metal clip having a "W" shaped cross-section. The clip is engageable with the head of the anchor bolt. An impact force applied in the direction of the axis of the bolt will deform the clip, thus reducing the peak impact force applied to the anchor bolt.